The invention relates to a method and apparatus for measuring left ventricular blood pressure, and more particularly to measuring left ventricular pressure from a pacing/defibrillation lead implanted in a branch vein of the coronary sinus. The measured left ventricular pressure may be used to adaptively control a pacing or defibrillation lead.
Heart disease (cardiomyopathy) can cause a patient to exhibit symptoms of congestive heart failure (CHF). CHF is a result of the weakening of the heart""s cardiac function characterized by reduced pumping capacity and efficiency. Chronic cardiac rhythm problems can also be the result of cardiomyopathy. The modification of the heart""s structure that causes the reduction in pumping capacity also causes modification of the heart""s electrical characteristics. The heart""s electrical pathways can become stretched out of shape and chemically damaged. This makes arrhythmias much more likely to occur in CHF patients.
Implantation of a pacemaker is a preferred method of treatment for arrhythmias in CHF patients. Although many types of heart problems may require a pacer, one method of treatment suited for CHF patients is known as cardiac resynchronization therapy (CRT). CRT uses a pacemaker with multiple pacing leads to coordinate the heart""s four chambers to act together in a sequence that will pump blood more efficiently.
It is likely that CRT candidates will have various forms of cardiomyopathy, and these patients may exhibit other measurable symptoms of reduced cardiac function besides arrhythmia. The reduced cardiac function of the heart is taken into account when applying CRT in order to tailor the treatment based on the needs of a particular patient. Various external factors must also be taken into account by the pacing system, one of those factors being the current state of activity of the patient.
Rate adaptive pacemakers are currently used that can estimate body activity by detecting body activity or breathing rate and depth, and therefore modify the pacing rate applied to the heart. These indicators can give a rough estimate of metabolic demand for a given patient. It would be beneficial to have more accurate measures of metabolic demand, especially measures that can determine the pumping capacity and pumping efficiency of a heart in order to measure and improve the efficacy of the therapy for the CHF patient.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading the present specification, there is a need in the art for improved ventricular monitoring and therapy control. There exists a further need for a pacing system that provides a means of measuring cardiac workload and efficiency in order to offer more effective treatment for CHF patients. The present invention fulfills these and other needs, and provides several advantages over prior systems and techniques.
The present invention is directed to a method and apparatus employing a pressure sensor in a body implantable pacing system. According to one embodiment of the present invention, a body implantable system includes a lead system having an open lumen, at least one electrode, and an occlusion device at a distal end of the lead system. A sensing catheter is movably disposed within the open lumen of the lead system. A distal tip of the sensing catheter extends beyond a distal tip of the lead system. The sensing catheter includes at least one pressure transducer at a distal end of the sensing catheter. A detection/energy delivery system is coupled to the lead system. The detection/energy delivery system senses ventricular rhythms from the electrode(s), senses pressure from the pressure transducer(s), and delivers an electrical signal to the electrode(s).
In one configuration, the pressure transducer includes a capacitive pressure sensor. In other configurations, the pressure transducer includes a piezoresistive pressure sensor, a micro-electrical-mechanical system (MEMS) pressure sensor and/or a resistive pressure sensor.
The detection/energy system may be configured to deliver a synchronized electrical signal to the electrode(s) for resynchronization therapy. The detection/energy system may also use a measured pressure from the pressure transducer(s) to adaptively modify the electrical signal sent to electrode(s).
The occlusion device of the lead system may include an increased diameter of the lead system at the distal end of the lead system. The occlusion device may also include an inflatable member at the distal end of the lead system. The inflatable member can include an absorbable material, the absorbable material inflating upon contact with a fluid. In another configuration, the inflatable member may inflate by injection of a fluid into the lead system.
According to another embodiment of the present invention, a method of pacing a patient""s heart involves implanting a lead system into a coronary vein of the patient""s heart. The lead system includes an open lumen, at least one electrode, and an occlusion device at a distal end of the lead system, the occlusion device occluding blood flow in the vein.
The method further involves introducing a sensing catheter within the open lumen of the lead system until a distal tip of the sensing catheter extends beyond a distal tip of the lead system. The sensing catheter includes at least one pressure transducer at a distal end of the sensing catheter. Ventricular electrical rhythms are measured from the electrode(s) to deliver a synchronized electrical signal to the electrode(s). A vein pressure is measured from the pressure transducer to adaptively modify the synchronized electrical signal.
Modifying the synchronized electrical signals can further involve measuring a timing between the measured coronary vein pressure and the measured ventricular electrical rhythms. Modifying the synchronized electrical signal can further involve modifying the synchronized electrical signal to minimize the pre-ejection period.
In one aspect of the method, a scaling factor is calculated between a measured coronary vein pressure and a left ventricular pressure. The scaling factor is applied before adaptively modifying the rate of the synchronized electrical signals.
According to another embodiment of the present invention, a method of pacing a patient""s heart involves implanting a first lead system into a coronary vein of the patient""s heart and a second lead system into a chamber of the patient""s heart. The first and second lead systems each include at least one electrode and at least one pressure transducer at respective distal ends of the lead systems.
The method further involves measuring ventricular electrical rhythms from the electrodes of the first and second lead systems to deliver synchronized electrical signals to the electrodes of the first and second lead systems. A coronary vein pressure is measured from the pressure transducer(s) of the first lead system and a heart chamber pressure is measured from the pressure transducer(s) of the second lead system to adaptively modify the synchronized electrical signals.
In one aspect of the method, the second lead system is implanted in the right ventricle, and adaptively modifying the synchronized electrical signals further involves measuring a right ventricular pressure from the pressure transducer(s) of the second lead system. Adaptively modifying the synchronized electrical signals can further involve adaptively modifying the synchronized electrical signals to minimize an area of a PP Loop derived from the measured right ventricular pressure and the measured coronary vein pressure.
In another aspect of the method, modifying the synchronized electrical signals can further involve measuring a timing between the measured coronary vein pressure and the measured ventricular electrical rhythms. Modifying the synchronized electrical signal can further involve modifying the synchronized electrical signal to minimize the pre-ejection period.
Modifying the synchronized electrical signals can further involve measuring a timing between the measured heart chamber pressure and the measured ventricular electrical rhythms. Modifying the synchronized electrical signal can further involve modifying the synchronized electrical signal to minimize an electromechanical timing period.